Encryption methods of many kinds are well known. One such method, known as the one time pad encryption method was invented in 1917 by Major Joseph Mauborgne and AT&T's Gilbert Vernam. The one time pad is a key of random letters, written on sheets of paper bound together in a pad. The pad is used to encrypt plain text and to decrypt the encrypted ciphertext. The pad is kept secret, and can be referred to as a private key. For security, the pad has the same or more letters than the message being encrypted. Accordingly, the pad is cumbersome, because it requires a large number of letters.
For securing encrypted files in a personal computer or terminal, the key used to encrypt the plain text or information may be stored within the physical system of the personal computer or in a network to which the personal computer is connected. This is disadvantageous because the security of the key can be breached by an individual having access to the particular personal computer or to the network to which the personal computer is coupled.